Japanese Patent Laying-Open No. 10-308510 (Patent Literature 1) discloses a semiconductor device having a substrate made of single-crystal silicon carbide. According to this publication, in order to manufacture this device, a silicon carbide epitaxial layer is formed on a main surface of a semiconductor substrate made of single-crystal silicon carbide, a surface channel layer is disposed on the silicon carbide epitaxial layer, and a gate electrode is formed over a surface of the surface channel layer with a gate insulating film interposed therebetween. As a method for forming such a gate insulating film, an oxidation step involving heating is illustrated.